1. Field of the Invention
The present invention relates to pressure fluid machines of the rotary kind in general, and more particularly to machines of this type that incorporate orbiting blades.
2. Description of the Related Art
There are already known various constructions of machines that will be collectively referred to herein as pressure fluid machines, that is machines that either compress or pump gases or liquids (generally referred to herein as pumps), or are powered either by pressurized or by expanding, combusting, exploding or otherwise chemically reacting fluids (generally referred to herein as engines). The term xe2x80x9cpumpsxe2x80x9d as used here includes those machines that compress or otherwise impart potential or kinetic energy to fluids, be they compressors, blowers or actual pumps, while the term xe2x80x9cenginesxe2x80x9d stands not only for those of the steam or internal combustion varieties but also for other fluid-powered machines that are ordinarily called motors or drives. Among the heretofore proposed pressure fluid machines, there are also those of the rotary type, that is those including rotors mounted for rotation in respective internal chambers of associated stators or housings.
Some rotors of such rotary engines or pumps include blades that orbit associated axes within the respective internal chambers, being ordinarily in frictional contact at their outer peripheral end faces with the surfaces bounding such chambers. Typically, in a machine of this type, the aforementioned axis is that of the internal chamber and also of a torque-transmitting (i.e. input or output, as the case may be) shaft traversing such chamber, and the rotor includes, besides the blades, a body that is mounted on the housing for eccentric turning or rotational movement about and relative to this axis or shaft and serves as a carrier or entrainment member for the blades. A known representative of this approach is to be found in the publication Grundzxc3xcge der Theorie und des Baues der Dampfturbinen mit der Berxc3xccksichtigung der Rotationsdmapfmaschinen, by Peter Stierstorfer, Leipzig, Germany (1904), in which page 139 reveals a so-called xe2x80x9cPatschkexe2x80x9d rotary steam engine. Its structure is characterized in that one of its blades is rigidly connected with the central shaft which thus becomes torque-transmitting in that the torque imparted to it by the one blade is transmitted thereby to the exterior of the engine and ultimately to a part or parts driven by this torque. In the course of the rotation of the rotor, the orbiting blade is retracted into or extended out of an associated opening provided for it in the entraining rotor member or body; this has for its consequence alternating changes in the working radius of this orbiting blade and simultaneously the latter is accelerated and subsequently decelerated during each rotation, depending on the angular position about the central axis at which it is situated at any particular time. Simultaneously with and as a direct consequence of the increase and decrease in the circumferential speed of the orbiting blade, even the speed of the torque-transmitting shaft varies accordingly in the course of the respective revolution, owing to the rigid connection of the one orbiting blade with the shaft. This causes non-uniform rotation and pulsation of this shaft. When the torque-transmitting shaft is subsequently subjected to an additional torque of, for instance, a drive machine and/or a driven wheel of a mobile machine, and/or by a simple increase in the energy level of the supplied medium in an expansion motor, or during the transmission of high compression ratios of the fluid media being pressurized in compressors, there is encountered an excessively high stressing at the region of the rigid connection between the orbiting blade and the torque-transmitting shaft. This disadvantageous repetitive stressing results in relatively high incidence of damage to the machine, reduces its useful life, and requires the performance of an arduous process in the selection of suitable materials.
Another known implementation of a rotary machine with orbiting blades involves loose accommodation of such blades in radial recesses formed at the outer periphery of the eccentrically mounted rotor body. This solution exhibits a plethora of disadvantages stemming basically from the fact that the centrifugal forces acting on the individual blades increase with increasing rotational speed of the rotor. As a result, the force with which each of them presses against the surface circumferentially bounding the internal chamber of the stator increases as well, and the frictional losses of the pressure fluid machine increase disproportionately. Then, there exists a limit on the rotational speed of the rotor for the machine to be able to perform its function, and when this limit is exceeded, the encountered friction forces consume all of the input energy and the machine rotor rotation is retarded up to the point of ceasing altogether. A further disadvantage of this solution is to be seen in the fact that there is merely a line contact between the outer peripheral surface of the respective orbiting blade and its counterpart on the stator, inasmuch as the orbiting blades are centered not on the central axis of the cylindrical working space or chamber of the stator, but rather on the axis of the eccentrically mounted rotor that is transversely offset from the central axis; this limits the use of the machine of this construction to just as a compressor.
Another technical solution that has a pronounced bearing on the present invention is disclosed in the European patent EP 0 102 555. This machine includes a hollow cylindrical stator housing in the interior of which there is eccentrically mounted a rotor body; the latter has mounted thereon, at its outer periphery, respective cylindrical guiding members for free turning relative to the rotor body about respective axes extending parallel to the central axis of the internal chamber of the chamber. A pivot axle centered on this axis is immovable relative to the stator housing. Orbiting blades pass through the respective guiding members to cooperate with the inner surface of the cylindrical stator housing. These blades extend substantially radially with respect to the central pivot axle, and their radial distance is adjustable by means of connecting rods that are rotatably supported on the central pivot axle.
Disadvantages of this solution are to be seen primarily in the existence of tilting moments arising as a consequence of asymmetrical support of the connecting rods on the central pivot axle, and in their implementation with an adjustable feature, which involves technical complexity and, in the event of thermal loading, low resistance to deformations. Another persisting drawback exists at the sealing locations, which are problematical especially at the interfaces between the orbiting blades and the rotor body, and between the outer peripheral surfaces of the blades and the inner surface bounding the internal chamber of the cylindrical stator housing. It is also necessary to offset the axial termination of the rotating part or rotor body from the corresponding portion of the stator housing facing the same, and a high gradient of the pressure medium exists at this region, with attendant high losses of such medium. Last but not least, the cantilevered mounting of the central pivot axle detracts from the mechanical stability of the machine.
Generally applicable disadvantages of the heretofore known rotary machine systems with orbiting blades include the existence of considerable frictional forces both between the orbiting blades and the rotor body and between the orbiting blades and the stator housing, as well as the existence of high material stresses at the connection locations of the orbiting blades and the torque-transmitting shaft. When the orbiting blades are loosely supported on the rotor body, frictional forces that are significantly increased with increasing speed of rotation are encountered even at the contact surface of the orbiting blade at its outer periphery with the surface bounding the internal chamber of the stator housing. In view of these drawbacks, the heretofore presented embodiments of these machines have been limited to rotary machines with a relatively large axial length of the rotor part accompanied by a relatively small diameter thereof, in which the frictional forces encountered are not yet too destructive, and in which there exists a better possibility of sealing the zones between the axial end faces of the rotating part and the corresponding surfaces of the stator part, especially in air expansion motors and air compressors, such as in the Wittig systems.
Accordingly, it is a general object of the present invention to avoid the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide a rotary machine that does not possess the drawbacks of the known of this type.
Still another object of the present invention is to devise a rotary machine of the type here under consideration in which power and speed pulsations encountered in similar conventional machines are kept to a minimum if not eliminated altogether.
It is yet another object of the present invention to design the above rotary machine in such a manner as to minimize frictional and other losses to enable its operation at extremely high throughput rates.
A concomitant object of the present invention is so to construct the of the above type as to be relatively simple in construction, inexpensive to manufacture, easy to use, and yet reliable in operation.
In keeping with the above objects and others which will become apparent hereafter, one feature of the present invention resides in an orbiting blade rotary machine, especially for use in compressor and expansion motor units, which includes a stator housing bounding an internal space that includes a substantially cylindrical internal chamber centered on a central axis. A power shaft extends in a centered relationship along the central axis through the internal space inclusive of its working chamber and is mounted on the stator housing for rotation about the central axis. Each of a plurality of orbiting blades extends substantially radially outwardly from the power shaft in the internal chamber toward the stator housing in a neutral position thereof and is supported for pivoting within a limited angular range around the neutral position relative to the power shaft. An eccentric rotor is mounted in the stator housing for rotation about an eccentric axis parallel to and transversely offset from the central axis and is accommodated in the internal chamber to delimit in it a working space that the orbiting blades subdivide into individual compartments. The eccentric rotor includes means for guiding the orbiting blades for sliding relative to the eccentric rotor while performing the limited pivoting relative to the power shaft. In accordance with the invention, there is further provided means for positively transmitting torque between the eccentric rotor and the power shaft; and means for sealing the interfaces between the orbiting blades and the stator housing.
The torque transmitting means advantageously includes at least one torque transmitting gear train including a crown gear rigid with the eccentric rotor, an auxiliary shaft mounted in the housing for rotation about an axis parallel to and transversely offset from the central axis, a first and a second auxiliary spur gear secured to the auxiliary shaft for joint rotation therewith, the first auxiliary spur gear being in permanent meshing relationship with the crown gear, and another spur gear secured to the power shaft for joint rotation therewith and permanently meshing with the second auxiliary spur gear. It is also advantageous when the eccentric rotor includes a pair of axially spaced carrier rings and a plurality of connecting bars interconnecting the carrier rings in substantial parallelism with the eccentric axis and including substantially part-circular cylindrical surfaces facing each other. Then, the guiding means advantageously includes a plurality of guiding cylinders, one for each of the orbiting blades, each accommodated in sealed relationship between the surfaces of the connecting bars for turning relative thereto and each including an axially and radially extending passage for receiving the respective one of the orbiting blades for sliding therein.
It is especially advantageous when the sealing means includes a labyrinth seal at least on a marginal portion of each of the orbiting blades that is remote from the power shaft. The sealing means may further include a channel system within at least each of the orbiting blades for supplying pressurized sealing fluid to the labyrinth seal.
A particular advantage of the present invention is that the construction proposed here renders it possible very effectively to eliminate mechanical friction between the rotating component and the stator housing. This friction elimination is primarily based on the possibility of providing the aforementioned remote marginal portions of the orbiting blades with the labyrinth seals; this possibility, in turn, is based on the constant radial dimension of each of the orbiting blades as it turns in the internal chamber about the central axis while being supported by respective bearing eyelets on the power shaft without being rigidly connected with it. The mounting of the orbiting blades on the power shaft by the respective eyelet pairs eliminates any tilting moment that could otherwise exist and makes possible operation at, for all intents and purposes, unlimited high r.p.m. speeds, without deleterious consequences that would otherwise arise from the action of centrifugal forces and resulting pressing of the blades against the stator housing surface bounding the internal chamber. This advantageous construction of the rotary machine makes it possible to use this rotary machine even in conditions calling for very high rotational speeds.
Another advantage of this construction resides in the accommodation of the axial end portions of the rotor in the end walls of the stator housing that bound the internal chamber; this makes it possible to provide even these zones of the orbiting blades with contactless labyrinth seals or seals exhibiting similar properties, which assures a highly effective suppression of pressure gradients at the regions in question and makes it possible to construct the machines of this type with a relatively small axial length but a relatively sizable diameter. As a result, this construction makes it possible to use the rotary machine for high power parameters and transmission of relatively high torques in the applications of such rotary machines not only in compressor units but also, and especially, in expansion motor units. The transmission of the torque between the power shaft and the rotor proper by means of the aforementioned auxiliary gear train assures uniform movement of the central power shaft without pulsation or oscillation. Last but not least, the structure of the rotary machine embodying the present invention makes it possible to provide a thermal machine operating on the basis of Brayton cycle with closed circulation of gas and with its external heating in the field of volumetrically operating machines, for instance in a combination of a compressor with an expansion motor. Such a combination of systems exhibits very advantageous ecological values as far as the exhaust gases are concerned, and the equipment is capable of operating at high efficiency ratios.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.